System and Method of Detecting Sleep Disorders

ABSTRACT

An apparatus for detecting sleep disorders, such as obstructive sleep apnea, includes a housing insertable into an ear canal of a subject. A sensor disposed within the housing measures a position of the subject&#39;s head relative to an axis of gravity. A transducer is responsive to the sensor and is capable of creating a stimulus detectable by the subject under certain conditions. In various embodiments, a controller receives signals corresponding to a pitch angle and a roll angle of the subject&#39;s head measured by the sensor, determines if the pitch and roll angles correspond to a sleep apnea inducing position, and causes the transducer to generate a stimulus upon determining that the subject&#39;s head is in the sleep apnea inducing position more than a predetermined threshold number of times. Various parameters of the stimulus may be modified with successive stimulus generation until a non-sleep apnea inducing position is detected.

FIELD OF THE INVENTION

This disclosure relates to techniques for detecting sleep disorderconditions, and, more particularly, to a system and method of detectingobstructive sleep apnea.

BACKGROUND OF THE INVENTION

Obstructive sleep apnea (OSA) is the most common category ofsleep-disordered breathing. In obstructive sleep apnea, the muscle toneof the body ordinarily relaxes during sleep. At the level of the throat,the human airway is composed of collapsible walls of soft tissue whichcan obstruct breathing during sleep. In some cases, obstructive sleepapnea requires treatment to prevent low blood oxygen, sleep deprivation,and other complications.

Some techniques to address sleep apnea involve sleeping at a 30-degreeor higher elevation of the upper body, as if sleeping in a recliner.Doing so helps prevent the airway from being blocked or obstructed.Furthermore, lateral positions (sleeping on a side), as opposed tosupine positions (sleeping on the back), are also recommended as atreatment for sleep apnea. Other treatments include the use ofcontinuous positive airway pressure (CPAP) or oral appliances to keepthe airway open during sleep.

Accordingly, there is a need for a sleep apnea detection apparatus thatmay alert the user when the user's head is positioned in the sleep apneainducing position.

SUMMARY OF THE INVENTION

Disclosed are technologies for detecting sleep apnea. According toembodiments of the disclosure, a sleep apnea detection apparatus isconfigured such that when the subject positions himself or herself in asleep apnea inducing position, the sleep apnea detection apparatus mayalert the subject by generating a stimulus, such as an audible alarm. Inthis way, the subject may adjust his or her position so that the subjectis no longer in the sleep apnea inducing position. A sleep apneainducing position may be any position assumed by the subject that causesthe subject to be prone to experiencing sleep apnea. It should beunderstood that even if a subject is positioned in a sleep apneainducing position, the subject may not experience sleep apnea. Generallyspeaking, obstructive sleep apnea occurs when the airway is obstructedor blocked to an extent that a user experiences sleep apnea. Theobstruction may be caused by the mass of the tongue or loosened musclesaround the throat. Regardless of what causes the obstruction, it hasbeen determined that the position of a subject's head relative to anaxis of gravity is related to the occurrence of obstructive sleep apnea.By way of the present disclosure, a subject may be alerted when thesubject assumes a sleep apnea inducing position by monitoring theposition of the subject's head using a sleep apnea detection apparatusthat includes a dual-axis inclinometer.

According to one aspect of the disclosure, a device for detecting sleepdisorders includes a housing that can be inserted into an ear canal of asubject. A sensor disposed within the housing measures a position of thesubject's head relative to an axis of gravity, while a transducer thatis responsive to the sensor, is capable of creating a stimulusdetectable by the subject. In various embodiments, a controller mayreceive signals corresponding to a pitch angle and a roll angle formedbetween an axis of the subject's head and the axis of gravity asmeasured by the sensor, determine if the pitch and roll anglescorrespond to a sleep apnea inducing position, and cause the transducerto generate a stimulus if the subject's head is in the sleep apneainducing position.

According to another aspect of the disclosure, a method for detectingsleep disorders includes providing a sensor that can be inserted intothe ear canal of a subject and measuring the position of the subject'shead relative to gravity. Based on the measured position of thesubject's head, a determination is made as to whether the subject's headis in a sleep apnea inducing position. If the subject's head isdetermined to be in the sleep apnea inducing position, the subject maybe alerted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of an sleep apnea detectionapparatus, in accordance with some embodiments of the presentdisclosure;

FIG. 2A illustrates a block diagram of a sleep apnea detection circuitin accordance with some embodiments of the present disclosure;

FIG. 2B illustrates a top view of the sleep apnea detection circuit on acircuit board in accordance with some embodiments of the presentdisclosure;

FIGS. 2C-D illustrate block diagrams of sleep apnea detection systems inaccordance with embodiments of the present disclosure;

FIGS. 3A and 3B illustrate a hypothetical subject's head and the threeorthogonal axes relative to the subject's head in accordance with thepresent disclosure;

FIG. 3C illustrates the perspective view of a conceptual inclinometerrelative to the three orthogonal axes in accordance with embodiments ofthe present disclosure;

FIGS. 4A-D illustrate a hypothetical subject's head oriented at variouspitch angles and a corresponding gravitational force acting on thesubject's airway in accordance with embodiments of the presentdisclosure;

FIG. 5A illustrates a conceptual representation of a hypotheticalsubject's head oriented at various pitch angles corresponding to thepitch angles of FIG. 4A-D in accordance with embodiments of the presentdisclosure;

FIG. 5B illustrates a conceptual representation of a hypotheticalsubject's head and a range of sleep apnea inducing pitch angles inaccordance with embodiments of the present disclosure;

FIG. 6 illustrates a plot of the airway crush force percentage over arange of pitch angles in accordance with embodiments of the presentdisclosure;

FIG. 7 illustrates a range of pitch angles in which the subject mayexperience sleep apnea in accordance with embodiments of the presentdisclosure;

FIG. 8A illustrates conceptual views of a subject's head oriented atvarious roll angles in accordance with embodiments of the presentdisclosure;

FIG. 8B illustrates a conceptual representation of a subject's head anda range of sleep apnea inducing roll angles in accordance with someembodiments of the present disclosure;

FIG. 9 illustrates a plot of the airway crush force percentage over arange of roll angles in accordance with some embodiments of the presentdisclosure;

FIG. 10 illustrates a range of roll angles in which the subject mayexperience sleep apnea in accordance with some embodiments of thepresent disclosure;

FIG. 11A illustrates side views of a subject's head and respectiveorientations of the sleep apnea detection apparatus in accordance withsome embodiments of the present disclosure;

FIGS. 11B-C are front and side views of a subject's head showing theorientation of the dual-axis inclinometer relative to the orthogonalaxes in accordance with some embodiments of the present disclosure;

FIG. 12 illustrates an exemplary logical flow diagram for calibrating asleep apnea detection apparatus in accordance with some embodiments ofthe present disclosure;

FIG. 13 illustrates an exemplary logical flow diagram for detectingwhether the subject is in a sleep apnea inducing position in accordancewith some embodiments of the present disclosure;

FIG. 14 illustrates an exemplary logical flow diagram for generating astimulus in response to the subject's position in accordance with someembodiments of the present disclosure;

FIG. 15 illustrates a plot of various signals corresponding to the pitchangle, the roll angle, and an output signal generated by amicrocontroller when the subject assumes supine positions that maximizethe effects of apnea in accordance with some embodiments of the presentdisclosure; and

FIG. 16 illustrates a plot of various signals corresponding to the pitchangle, the roll angle, and an output signal generated by amicrocontroller when the subject assumes non-supine positions thatminimize the effects of apnea in accordance with some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure will be more completely understood through thefollowing description, which should be read in conjunction with theattached drawings. In this description, like numbers refer to similarelements within various embodiments of the present disclosure. Theskilled artisan will readily appreciate that the methods and systemsdescribed herein are merely exemplary and that variations can be madewithout departing from the spirit and scope of the disclosure.

Referring now to the figures, FIG. 1 illustrates a perspective view of asleep apnea detection apparatus 100 in accordance with some embodimentsof the present disclosure. The sleep apnea detection apparatus 100 mayinclude a housing 110 having an ear insertion end 120 and an apparatusaccess end 130. The housing 110 is shaped so that the ear insertion end120 of the apparatus 100 can be at least partially inserted into the earcanal of a subject. Further, the housing 110 may be made from any of awide range of materials that may be rigid, semi-rigid, or flexible, suchthat when the apparatus 100 fits comfortably into the ear canal ofsubjects. The ear insertion end 120 may be sized such that an optimalprotective cover (not shown) may surround a portion of the ear insertionend 120. The protective cover may be made of a material that adjusts insize to ensure that the sleep apnea detection apparatus 100 is snuglyfit within the ear canal of the subject. In one embodiment, theprotective cover may be made from COMPLY® foam tips, commerciallyavailable from the website http://www.complyfoam.com. It should beappreciated that the protective cover may be removed for disposal,replaceable or washable to reduce the risk of an ear infection. However,the sleep apnea detection apparatus 100 may still be operable withoutthe use of the protective cover.

The apparatus access end 130 of the apparatus 100 provides access to aninterior chamber defined within the housing 110. In various embodiments,the apparatus access end 130 may be configured to receive a sleep apneadetection circuit 200 that is configured to detect whether the subjectwearing the sleep apnea detection apparatus 100 is in a sleep apneainducing position. Additional details regarding the sleep apneadetection circuit 200 are provided with respect to FIG. 2.

The apparatus access end 130 may include an at least partially movableor removable cover 132 in which a power source 134, such as a battery, acell, or any other electrical power storage component may be placed. Itshould be appreciated that the power source 134 (shown in FIG. 2) may berechargeable and/or removable. In addition, the sleep apnea detectionapparatus 100 includes a switch 136 that controls the power beingsupplied to various components of the sleep apnea detection circuit 200from the power source 134.

The apparatus access end 130 may also include a rotational component 138that may be configured to rotate the sleep apnea detection circuit 200within the interior chamber of the housing 110 in at least two planes.The rotational component 138 may include one or more accessible setscrews which may be rotated to adjust the orientation of the sleep apneadetection circuit 200 with respect to the housing 110. The ability toadjust the orientation of the sleep apnea detection circuit 200 enablesthe circuit to be reoriented as the size, shape, and structure of earcanals of various subjects may vary. Additional details regarding thecalibration of the sleep apnea detection apparatus 100 with respect to aparticular subject are provided below with respect to the FIGS. 11 and12.

Although various embodiments of the present disclosure disclose a sleepapnea detection apparatus 100 that is designed to be disposed within anear canal of a subject, the scope of the present disclosure is notlimited to such embodiments. Rather, in some embodiments, the sleepapnea detection apparatus may be configured so as to be placed anywhereon the subject's head so as to detect various head positions relative tothe rest of the subject's body. For instance, the sleep apnea detectionapparatus may be designed to be strapped around the subjects forehead,worn as a peakless cap or hat, or be positioned on the outside of thesubject's ear. Other non-limiting examples include a device insertablein the mouth, nose, or attachable to the subject's hair, amongst others.

FIG. 2A illustrates a block diagram of an exemplary sleep apneadetection circuit 200 in accordance with some embodiments. As describedabove, the sleep apnea detection circuit 200 may be positioned withinthe interior chamber of the housing 110. It should be appreciated thatthe sleep apnea detection circuit 200 may be packaged as a single ICpackage that may be inserted in the interior chamber of the housing 110.FIG. 2B illustrates a top view of the sleep apnea detection circuit 200on a circuit board 220 in accordance with some embodiments of thepresent disclosure. Referring now to FIGS. 2A and 2B, the sleep apneadetection circuit 200 may include a microcontroller 202 that isconfigured to receive power from a DC-DC converter 204. The DC-DCconverter 204 may be configured to receive power from the power source136 and convert the voltage provided by the power source 136 to avoltage suitable for the microcontroller 202. The microcontroller 202may be electrically coupled to a sensor, including but not limited to agravitational sensor, such as a three axis inclinometer, a dual-axisinclinometer 206 or a single-axis inclinometer, and one or more bufferamplifiers 208, such that the microcontroller 202 may be able to supplypower to the dual-axis inclinometer 206 and the buffer amplifiers 208.The dual-axis inclinometer 206 may be configured to output a firstsignal corresponding to a measured pitch angle and a second signalcorresponding to a measured roll angle. In addition, the microcontroller202 may be able to receive the first and second signals generated by thedual-axis inclinometer 206. In various embodiments, the dual-axisinclinometer 206 may be coupled to the buffer amplifiers 208, such thatthe signals generated by the dual-axis inclinometer 206 may be amplifiedby the buffer amplifiers 208 and provided to the microcontroller 202 asinput signals.

The microcontroller 202 may be configured to execute one or morealgorithms directed towards calibrating the sleep apnea detectionapparatus 100, as well as algorithms for determining whether a subject'shead is positioned in a sleep apnea inducing position, and generating astimulus upon determining that the subject's head is in a sleep apneainducing position.

The microcontroller 202 may also be configured to provide an outputsignal that may generate a stimulus indicating that the subject's headis in a sleep apnea inducing position. In one embodiment, themicrocontroller 202 may provide an output signal to a bandpass filterand attenuator 210, which passes the output signal to a transducer 212.In various embodiments the transducer 212 may be speaker, a tonegenerator, a vibration generator, or any other stimulus generatingcomponent It should be appreciated that the transducer 212 may becapable of generating haptic stimulus and/or audible stimulus that isdetectable by the subject.

In one embodiment, microcontroller 202 may be implemented as a 16 PINQFN 4*4*0.9 mm BIT CMOS microcontroller having a part numberPIC16F684-1/ML commercially available from Microchip Technology, Inc,Chandler, Ariz. The tri-axis accelerometer used as a dual-axisinclinometer 206 may be implemented with a model KXTC9 accelerometercommercially available from KIONIX®, Ithaca, N.Y. It should beappreciated that various other electrical components, including but notlimited to, capacitors, inductors, resistors, and potentiometers may beincluded as part of the sleep apnea detection circuit 200. Inparticular, a potentiometer may be coupled to the receiver 212 to adjustthe amplitude of the signal being generated. Additionally, oralternatively, the amplitude of the signal can be adjusted using otherelectrical components or through the microcontroller 202 itself.

The dual-axis inclinometer 206 can generate signals that are indicativeof the inclinometer's orientation relative to relative to gravity.Typically, a dual-axis inclinometer is capable of sensing angularposition in two directions relative to the direction of thegravitational force. In utilizing a dual-axis inclinometer to detectwhether a subject's head is in a sleep apnea inducing position, thesleep apnea detection apparatus 100 may be configured to measure theangular position of the subject's head relative to one or moreorthogonal axes. In various embodiments, the inclinometer 206 utilizesan axis representing the instantaneous direction of gravity, referred tohereinafter generally as gravity axis, as one of the orthogonal axes.

As described above, the dual-axis inclinometer 206 may output a firstsignal corresponding to a pitch angle and a second signal correspondingto a roll angle. The microcontroller 202 may be configured to comparethe first signal with threshold values that correspond to apredetermined range of pitch angles that may induce sleep apnea. Thispredetermined range of pitch angles is referred to as sleep apneainducing pitch angles. The microcontroller 202 may also be configured tocompare the second signal with threshold values that correspond to apredetermined range of roll angles that may induce sleep apnea. Thispredetermined range of roll angles is referred to as sleep apneainducing roll angles. In typical embodiments, a subject can experiencesleep apnea when the first signal corresponds to a pitch angle that lieswithin the sleep apnea inducing pitch angles, and the second signalcorresponds to a roll angle that lies within the sleep apnea inducingroll angles.

If both the pitch angle and roll angle formed between the subject's headand the corresponding reference axis lie within sleep apnea inducingpitch angles and sleep apnea inducing roll angles, respectively, themicrocontroller 202 may generate an output signal that causes thetransducer 212 to generate a stimulus that is detectable by the subject.Additional details regarding the sleep apnea inducing pitch angles willbe provided with respect to FIGS. 4-6 and sleep apnea inducing rollangles will be provided with respect to FIGS. 7-9.

Although the present disclosure describes embodiments of a sleep apneadetection apparatus that does not record data, it should be appreciatedthat the apparatus may be configured to do so. In some embodiments, thesleep apnea detection apparatus 100 may be designed for variousapplications, such as conducting sleep analysis studies, remotelymonitoring a subject sleep, and the like. As such, sleep clinics may usethe sleep apnea detection apparatus to analyze the various headpositions in which a subject may fall asleep, as well as determine thesubject's head positions in which the subject experiences sleep apnea.As such, there may be a desire to record the data generated by thedual-axis inclinometer 206 while a subject is asleep.

Referring now to FIG. 2C, a sleep apnea detection system may include alocal sleep apnea detection circuit 200C that resides in the housing110. The local sleep apnea detection circuit 200C is similar to thesleep apnea detection circuit 200, but differs in that there is nomicrocontroller 202. Instead, the local sleep apnea detection circuit200C includes an interface 242 that allows a data output port 216 toreceive the output signals generated by the dual-axis inclinometer andsend the information associated with the output signals to a remotesleep apnea processing unit 220. The remote sleep apnea processing unit220 may include a communications port 224 communicatively coupled to thedata output port 216. In addition, the remote sleep apnea processingunit may include a processor 222 that can process the signals receivedfrom the local sleep apnea detection circuit 200C and store associateddata in a storage location, such as storage 226. In addition, the remotesleep apnea processing unit 220 may provide the output signal to abandpass filter and attenuator 230, which passes the output signal to atransducer 232, which is capable of alerting the subject.

Referring now to FIG. 2D, a sleep apnea detection system may include alocal sleep apnea detection circuit 200D that resides in the housing110. The local sleep apnea detection circuit 200D is similar to thesleep apnea detection circuit 200, but differs in that themicrocontroller 202 is coupled to a data output port 216, which canprovide the output signals generated by the dual-axis inclinometer 206to a remote sleep apnea processing unit 250. The remote sleep apneaprocessing unit 250 may include a communications port 254communicatively coupled to the data output port 256. In addition, theremote sleep apnea processing unit may include a processor 252 that canprocess the signals received from the local sleep apnea detectioncircuit 200D and store associated data in a storage location, such asstorage 256.

In various embodiments, the sleep apnea detection apparatus 100 mayinclude a data port 214 through which data from the sleep apneadetection circuit 200 can be transferred to an external storagelocation, including but not limited to, a computer configured to recordsuch data. The data port may be configured for wired data transfer orwireless data transfer, using technologies, including but not limitedto, BLUETOOTH, short range wireless data transmission, or other forms ofdata transmission. In some embodiments, the data storage location may belocated near the subject, while in other embodiments, the data storagelocation may be located at a remote location. In some embodiments, thesleep apnea detection apparatus may be configured to access acommunications network, such as WiFi, LAN, WAN, or any othercommunications network through which the data generated by the dual-axisinclinometer 206 can be transferred to the storage location. In variousembodiments, the sleep apnea detection circuit may simply be configuredto poll the dual-axis inclinometer 206 for readings, and the outputsignals from the inclinometer 206 may be provided to an externalprocessing system, which can process the data and generate a stimulusthat can get the attention of the subject. Utilizing either of theconfigurations illustrated in FIG. 2C-D, it should be understood thatthe communications between the sleep apnea detection apparatus and thesleep apnea processing unit may be bi-directional. directional. Forexample, using any of the above identified communications protocols, thedata from inclinometer 206 may be either pushed to or pulled byprocessor 222. Utilizing the configuration illustrated in FIG. 2D, thesignal to initiate transducer 212 may originate from processing unit 220in response to data transmitted to unit 220 from unit 200C and evaluatedby processor 222.

A subject is capable of rotating his or her head 302 about any of threefixed orthogonal axes. For the sake of clarity, FIGS. 3A and 3Billustrate a subject's head 302 and the three fixed orthogonal axesrelative to which the subject's head 302 can rotate. Throughout thepresent disclosure and as shown in FIG. 3A, the three fixed orthogonalaxes can be described relative to a hypothetical subject lying in asupine position and looking straight ahead. An x-axis 306 extends fromthe top of the hypothetical subject's head to the bottom of thehypothetical subject's head such that when the hypothetical subject isstanding upright, the x-axis 306 is aligned with an instantaneous axisof gravity. As shown in FIG. 3B, the y-axis 308 refers to an axis thatextends from one ear of the hypothetical subject's head to the otherear, and the z-axis 310 refers to an axis that extends from the nose ofthe hypothetical subject's head 302 to the back of the hypotheticalsubject's head 302. It should be appreciated that when the hypotheticalsubject is lying down in the supine position, the z-axis 310 is alignedwith the instantaneous direction of gravity.

Rotation of the subject's head 302 about the x-axis 306 is referred toherein as roll, and an angle formed between an axis extending from thenose 304 of the subject's head 302 to the back of the subject's head 302and the y-axis 308 is referred to herein as the roll angle. Rotation ofthe subject's head 302 about the y-axis 308 is referred to herein aspitch, and an angle formed between an axis extending from the nose ofthe subject's head 302 to the back of the subject's head 302 and thez-axis 310 is referred to herein as the pitch angle. Rotation of thesubject's head 302 about the z-axis 310 is referred to herein as yaw,and an angle formed between an axis extending from the top of thesubject's head 302 to the bottom of the subject's head 302 and thex-axis 306 is referred to herein as the yaw angle. It should beappreciated that any of the axes 306, 308, 310 may or may not be alignedwith the axis of gravity. In embodiments, where none of the axes 306,308, 310 are aligned with the axis of gravity, corrective adjustmentscan be made in the sleep apnea detection circuit to compensate for themisalignment.

As described above, obstructive sleep apnea is a condition in whichpauses in breathing occur during sleep because the airway has becomenarrowed, blocked, or floppy. During sleep, a subject's muscles becomemore relaxed, including the muscles that help keep the airway open andallow air to flow into the lungs. Normally, the upper throat stillremains open enough during sleep to let air pass. However, some peoplehave a narrower throat area. When the muscles in their upper throatrelax during sleep, their breathing can stop for a period of time,oftentimes for more than 10 seconds. The stoppage of breathing is calledapnea. It should be appreciated that obstructive sleep apnea can becaused by the tongue forcing the soft palate to obstruct the airway, orby the tongue directly obstructing the airway.

It has been determined that the position of the subject's head 302relative to the axis of gravity is related to occurrences of obstructivesleep apnea. Positions in which a subject is likely to experience sleepapnea are referred to as sleep apnea inducing positions. A subject islikely to experience sleep apnea when the subject's head 302 ispositioned such that a pitch angle formed by an axis of the subject'shead 302 and the z-axis 310 that lies within a range of sleep apneainducing pitch angles and a roll angle formed by an axis of thesubject's head 302 and the y-axis 308 that lies within a range of sleepapnea inducing roll angles. The correlation of the position of asubject's head and sleep apnea is tied to the effect gravitationalforces have in causing the tongue 324 and/or the soft palate 322 toobstruct the airway 320. In particular, the direction in which gravityexerts a force on the tongue 324 and the soft palate 322 dictates theoccurrence of the airway being obstructed. Even though the overallmagnitude of gravitational force is constant under gravity, themagnitude of the gravitational force that causes the tongue 324 and thesoft palate 322 to obstruct the airway 320 changes as the position ofthe subject's head changes. Accordingly, certain head positions are morelikely than others to cause an occurrence of obstructive sleep apnea.

Typically, when the subject is in a supine position and looking straightahead along the z-axis 310, the gravitational forces acting on thetongue 324 and the soft palate 322 that can cause the airway 320 to beobstructed are at a maximum. The relationship of the airway crush forceand the pitch angle ⊖_(p) can be given by Equation 1 below

F=m*a*sin(⊖_(p))   (Equation 1)

where F is the airway crush force, m is the effective mass of tonguetissue, a is the acceleration due to gravity, and ⊖_(p) is the pitchangle, which is measured relative to the z-axis 310. Similarly, therelationship of the airway crush force and the roll angle ⊖_(r) can begiven by Equation 2 below:

F=m*a*sin(⊖_(r))   (Equation 2)

where F is the airway crush force, m is the effective mass of tonguetissue, a is the acceleration due to gravity, ⊖_(r) is the roll angle,which is measured relative to the y-axis 308.

FIGS. 4A-D illustrate a subject's head oriented at various pitch anglesand a corresponding gravitational force acting on the subject's airwayin accordance with some embodiments of the present disclosure. Inparticular, FIG. 4A illustrates the subject's head 302 in a supineposition such that the pitch angle ⊖_(p) formed between an axisextending from the top of the subject's head to the bottom of thesubject's head 302 and the z-axis 310 is 90°. When the pitch angle ⊖_(p)is 90°, the airway crush force is at a maximum. FIG. 4B illustrates thesubject's head 302 in an upright position, such that the pitch angle⊖_(p) formed between an axis extending from the top of the subject'shead to the bottom of the subject's head 302 and the z-axis 310 is 180°.When the pitch angle ⊖_(p) is 180°, the airway crush force is at aminimum, as explained by the equation provided above. FIG. 4C shows thesubject's head at a pitch angle that lies between 90°<⊖_(p)<180°, inwhich case only a portion of the total airway crush force is directedtowards forcing the tongue 324 or soft palate 322 to obstruct the airway320. FIG. 4D shows the subject's head at a pitch angle ⊖_(p)=270°, inwhich case the gravitational force acts upon the walls 322 of the airway320 in the opposite direction such that the airway 320 remains open.

FIG. 5A illustrates conceptual views of a subject's head at variouspitch angles corresponding to the pitch angles of the subject's headwith respect to FIGS. 4A-D. FIG. 5B illustrates a range of sleep apneainducing pitch angles relative to the z-axis 310. As shown in FIG. 5B,the range of sleep apnea inducing pitch angles may extend from 20° to160°.

FIG. 6 illustrates a plot of the airway crush force percentage over arange of pitch angles in accordance with some embodiments of the presentdisclosure. As described above, the relationship of the airway crushforce and the pitch angle ⊖_(p) is given by Equation 1.

As described above with respect to FIGS. 4 and 5, a subject may sleep ina supine position, in which the pitch angle formed by the subject's headis 90°. Although the subject may sleep at pitch angles slightly lessthan 90°, angles much smaller than 90° may be uncomfortable andundesirable. Accordingly, in some embodiments, a more practical range ofsleep apnea inducing pitch angles may be at approximately 75° orgreater.

FIG. 7 illustrates a range of pitch angles in which the subject mayexperience sleep apnea in accordance with some embodiments of thepresent disclosure. The sleep apnea detection circuit 200 may beconfigured to generate a stimulus when the pitch angle and the rollangle both lie within a range of sleep apnea inducing pitch angle androll angle positions, respectively. The range of sleep apnea inducingpitch angles may correspond to angles associated with a thresholdpercentage of the maximum airway crush force that can be exerted tocause the airway 320 to be obstructed and cause sleep apnea.

It has been determined that sleep apnea may occur when the airway crushforce causes the airway to be obstructed by either the tongue 324 or thesoft pallet 322. In various embodiments, the threshold percentage atwhich the airway is obstructed may be 35%, which corresponds to pitchangles that are greater than approximately 20° and less thanapproximately 160°. In other embodiments, the threshold percentage maybe 40%, which corresponds to pitch angles that are greater thanapproximately 25° and less than approximately 155°. In yet anotherembodiment, threshold percentage may be 50%, which corresponds to thepitch angles that are greater than approximately 30° and less thanapproximately 150°. It should be appreciated that as the thresholdpercentage increases, the likelihood of sleep apnea occurring alsoincreases. Moreover, the range of pitch angles also gets narrower as thethreshold percentage increases as well. It should also be appreciatedthat the angles that define the range do not necessarily have to add upto 180°. Rather, a range of pitch angles that induce sleep apnea mayextend from approximately 60° to 150°.

FIG. 8A illustrates conceptual views of a subject's head oriented atvarious roll angles in accordance with some embodiments of the presentdisclosure. In particular, FIG. 8A shows the subject's head rotatingabout the x-axis 306, such that the roll angle ⊖_(r) relative to they-axis 308 increases from 0° to 180° as the subject rolls his head fromhis right side to his left side, or if the subject rolls his head andbody from his right side to his left side. As shown in FIG. 8B, a rangeof sleep apnea inducing roll angles is shown, extending from 25° to 155°relative to the y-axis 308.

Although possible sleep apnea inducing positions may include roll anglesthat extend from approximately 12° to 168° relative to the y-axis 308,the sleep apnea detection apparatus 100 may be configured such that thesleep apnea detection apparatus 100 considers roll angles that rangefrom approximately 25° to 155° to lie within the range of sleep apneainducing positions, as indicated in FIG. 8B. This is because a subject,while sleeping, may not be able to maintain the roll angle less than 12°or greater than 168° relative to the y-axis 308. However, by includingthese ranges of angles within the sleep apnea inducing range, theaccuracy of the sleep apnea detection apparatus 100 may be degraded.However, it should be appreciated that in various embodiments, theseangles may be included within the range of angles that the sleep apneadetection apparatus 100 considers to lie within the sleep apnea inducingrange.

FIG. 9 illustrates a plot of the airway crush force percentage over arange of roll angles in accordance with some embodiments of the presentdisclosure. As described above, the relationship of the airway crushforce and the roll angle ⊖_(r) is given by Equation 2.

It has been determined that sleep apnea may occur when the airway crushforce exceeds a threshold percentage of the airway crush force. Invarious embodiments, the threshold percentage may be 35%, whichcorresponds to roll angles that are greater than approximately 20° andless than approximately 160°. In other embodiments, the thresholdpercentage may be 40%, which corresponds to roll angles that are greaterthan approximately 25° and less than approximately 155°. It yet anotherembodiment, threshold percentage may be 50%, which corresponds to thepitch angles that are greater than approximately 30° and less thanapproximately 150°. It should be appreciated that as the thresholdpercentage increases, the likelihood of sleep apnea occurring alsoincreases. Moreover, the range of roll angles also gets narrower as thethreshold percentage increases as well.

The sleep apnea detection apparatus 100 may not generate a stimulus aslong as the subject assumes a position in which the pitch angle ⊖_(p)does not lie within the pitch angle range of sleep apnea inducingpositions or the roll angle ⊖_(r) does not lie within the roll anglerange of sleep apnea inducing positions that are predefined in the sleepapnea detection circuit 200. In one embodiment, pitch angles that doesnot lie within the pitch angle range of sleep apnea inducing positionsinclude pitch angles that exceed 160° or are less than 20° relative tothe z-axis 310. It should be appreciated that even though some angles donot induce sleep apnea, sleeping in such positions may may beundesirable or uncomfortable. For instance, sleeping at pitch anglesless than 90° or pitch angles greater than 270° relative to the z-axis310 may be uncomfortable or undesirable. Similarly, roll angles thatdoes not lie within the roll angle range of sleep apnea inducingpositions include roll angles that are less than 20° or exceed 160°relative to the y-axis 308. It should be appreciated that it may not bepossible for a typical human to sleep at roll angles that exceed 250° orare less than −70°. However, since the sleep apnea detection apparatusis configured to only determine whether a subject is positioned in asleep apnea inducing position, no action is taken when the subject'shead is positioned at any angle that does not lie within the range ofangles that induce sleep apnea.

The sleep apnea detection apparatus 100 can generate a stimulus when thesubject assumes a position in which the pitch angle ⊖_(p) lies within arange of sleep apnea inducing positions, such as pitch angles that liebetween approximately 20° and 160° relative to the z-axis 310, and theroll angle ⊖_(r) is between approximately 20° and 160° relative to they-axis 308.

FIG. 10 illustrates a range of roll angles in which the subject mayexperience sleep apnea in accordance with some embodiments of thepresent disclosure. As described above, the sleep apnea detectioncircuit 200 may be configured to generate a stimulus when the pitchangle and the roll angle both lie within a range of sleep apnea inducingpitch angle and roll angle positions respectively. The range of sleepapnea inducing roll angles may correspond to roll angles associated witha threshold percentage of the maximum airway crush force that can beexerted to cause the airway 320 to be obstructed and cause sleep apnea.

It has been determined that sleep apnea may occur when the airway crushforce causes the airway to be obstructed by either the tongue 324 or thesoft pallet 322. In various embodiments, the threshold percentage atwhich the airway is obstructed may be 35%, which corresponds to rollangles that are greater than approximately 20° and less thanapproximately 160°. In other embodiments, the threshold percentage maybe 40%, which corresponds to roll angles that are greater thanapproximately 25° and less than approximately 155°. It yet anotherembodiment, threshold percentage may be 50%, which corresponds to theroll angles that are greater than approximately 30° and less thanapproximately 150°. It should be appreciated that as the thresholdpercentage increases, the likelihood of sleep apnea occurring alsoincreases. Moreover, the range of roll angles also gets narrower as thethreshold percentage increases as well. It should also be appreciatedthat the angles that define the range do not necessarily have to add upto 180°. Rather, a range of roll angles that induce sleep apnea mayextend from 60° to 150°.

Although the present disclosure discloses the use of a dual-axisinclinometer 206 to determine the pitch and roll angles of a subject'shead, other types of inclinometers, accelerometers, gyroscope or sensorsmay be utilized to determine the orientation of the subject's headrelative to the three fixed axes 306, 308, 310. In various embodiments,a single-axis accelerometer may be utilized. In particular, asingle-axis accelerometer is capable of providing angular informationrelated to a first axis, and angular information with reducedsensitivity in a second axis of the other two mutually orthogonal axes.Since the single axis accelerometer is capable of generating differentsets of output voltages along two separate axes, a single axisaccelerometer may be used as long as the range of pitch angles thatdefine the sleep apnea inducing positions and the range of roll anglesthat define the sleep apnea inducing positions are the same.

From FIGS. 6 and 9, it can be appreciated that the sleep apnea inducingpositions can be defined by pitch angles and roll angles that are thesame. For instance, the pitch angle range may be set at 20°<⊖_(p)<160°and the roll angle range may be set at 20°<⊖_(r)<160° off of theirrespective axes. In one embodiment, the sleep apnea inducing pitch angleposition may be set at 30° off of the x-axis 306, which may correspondto a threshold output voltage generated by the single-axisaccelerometer. As the subject's head moves towards a supine position androlls his head from 0°<⊖_(r)<180°, the sleep apnea detection circuit maygenerate a stimulus as the voltage outputted by the single-axisaccelerometer reaches the threshold output voltage. Since the thresholdoutput voltage correlates to a roll angle of approximately 30° relativeto the y-axis 308 or 150° relative to the y-axis 308, the stimulus canbe generated when the roll angle is within the range of sleep apneainducing positions.

The orientation of the dual-axis inclinometer 206 may be an importantconsideration for the accurate and consistent functioning of the sleepapnea detection apparatus 100. The dual-axis inclinometer 206 generatesoutput signals indicating the relative orientation of the sleep apneadetection apparatus 100 relative to the three fixed orthogonal axes 306,308, 310. Since the microcontroller 206 is designed to generate astimulus when the subject's head 302 assumes a sleep apnea inducingposition, it is important to make sure that the dual-axis inclinometer206 is generating output signals that accurately correspond to the rightroll angles and pitch angles. The overall accuracy of the apneadetection apparatus 100 is set by both a rotational error and aplanarity error, when placed in the ear.

The rotational error is associated with the pitch angle. In variousembodiments, acceptable ranges of the rotational error may include pitchangles that are between 170° and 190° relative to the axis of gravity.The rotational error can be easily removed during calibration as thesubject rotates the sleep apnea detection apparatus 100 within the earcanal about the axis of gravity until the pitch angle lies between 170°and 190° relative to the axis of gravity. In various embodiments, duringa calibration process, the sleep apnea detection apparatus may generatea stimulus indicating that the sleep apnea detection apparatus is notcalibrated. As the apparatus 100 is rotated within the ear canal of thesubject, the sleep apnea detection apparatus 100 may generate adifferent stimulus indicating that the apparatus no longer has arotational error. In various embodiments, the sleep apnea detectionapparatus may be configured to factor the rotational error whendetermining whether the subject's head 302 lies within in a sleep apneainducing pitch angle range.

Referring now to FIG. 11A, side views of a subject's head and respectiveorientations of the sleep apnea detection apparatus 100 are shown. Asubject may assume a sleep apnea inducing position based on theorientation of the subject's head. In particular, the subject may assumea sleep apnea inducing position when the subject's head assumes aposition in which the pitch angle lies within the sleep apnea inducingrange of pitch angles, and, the roll angle lies within the sleep apneainducing range of roll angles. As described above, since the sleep apneadetection apparatus 100, which contains the dual-axis inclinometer 206,is at least partially inserted within the ear canal of the subject,pitch and roll movements of the subject's head relative to the fixedorthogonal axes 306, 308 may change the orientation of the dual-axisinclinometer 206 relative to the two fixed orthogonal axes 306, 308.Accordingly, the output signal generated by the dual-axis inclinometer206 may also change, reflecting changes in the pitch and roll angles.

Prior to first use of the sleep apnea detection apparatus, a calibrationprocess may be performed since the dual-axis inclinometer determinespitch and roll angles relative to gravity or vertical. As such, when thesleep apnea detection circuit 200 including the dual-axis inclinometer206 is positioned within a subject's ear canal, the dual-axisinclinometer 206 can provide pitch and roll angles relative to the twoorthogonal axes. As part of the calibration process, which will bedescribed with respect to FIG. 12, the rotation angle of the dual-axisinclinometer 206 may lie within approximately 170° and 190° relative tothe gravity axis 306, as indicated in FIG. 11A. Depending upon whetherthe subject wears the sleep apnea detection apparatus 100 in their leftear or right ear, the sleep apnea detection circuit 200 positionedwithin the housing 110 may be rotated 180° relative to the housing 110.

As described above, the overall accuracy of the apnea detectionapparatus 100 may also depend on a planarity error. A planarity errorarises when the dual-axis inclinometer 206 is not aligned with each ofthe three orthogonal axes. Aligning the dual-axis inclinometer 206perpendicular to a line drawn from ear to ear, however is not as easy tocalibrate, detect, or adjust, as the planarity error varies based on theshape of the subject's ear canal. Planarity can be detected using agyroscope, which in itself would require calibration. Because the shapeand angle of each individual's ear canal may vary slightly from subjectto subject, a one-time planarity adjustment to match the subject'sunique ear canal orientation may be required. This one-time adjustmentmay be performed by the subject or by a doctor by rotating the sleepapnea detection circuit 200 within the housing 110. As described above,the rotational component 138, such as a set screw, accessible from theaccess end 130 of the sleep apnea detection apparatus 100 can rotate thesleep apnea detection circuit 200 relative to the housing 110. Invarious embodiments, separate screws may be used to rotate theinclinometer 206, or the sleep apnea detection circuit 200 within thehousing 110, about a particular axis.

FIGS. 11B-C are front and side views of a subject's head showing theorientation of the dual-axis inclinometer relative to the orthogonalaxes in accordance with some embodiments of the present disclosure. Byrotating the sleep apnea detection circuit 200 within the housing 110,the orientation of the dual-axis inclinometer 206 also changes. Toeliminate planarity errors, the dual-axis inclinometer 206 may beoriented such that the dual-axis inclinometer is aligned with the threefixed orthogonal axes 306, 308, 310.

FIG. 12 illustrates an exemplary logical flow diagram for calibratingthe sleep apnea detection apparatus 100 in accordance with someembodiments of the disclosure. A routine 1200 begins at operation 1202,where the sleep apnea detection apparatus 100 is powered on. In variousembodiments, the switch 136 may be configured to control the power beingsupplied to the sleep apnea detection apparatus 100. From operation1202, the routine 1200 proceeds to operation 1204, where themicrocontroller 202 determines whether the voltage being supplied by thepower supply 132 is greater than a threshold voltage. If themicrocontroller 202 determines that the voltage supplied by the powersupply is not greater than the threshold voltage, the routine 1200proceeds to operation 1206, where the microcontroller 202, viatransducer 216, such as with a speaker, generates a stimulus indicatinga low voltage. In various embodiments, the stimulus indicating a lowvoltage may be a signal having a specific frequency, amplitude andduration. For instance, the signal may be a 30 Hz signal that isgenerated for 2 seconds. In various embodiments, the threshold voltagemay be set as a voltage that can provide power to the microcontroller202, such that the microcontroller 202 can operate normally for apredetermined amount of time, for example, eight hours. It should beappreciated that the amount of power used by the microcontroller 202 maybe based, in part on, how frequently the microcontroller 202 polls thedual-axis inclinometer 206 for pitch angle and roll angle information,as well as the frequency and duration for which stimuli are generated bythe transducer 216.

From operation 1206, the routine 1200 proceeds back to operation 1202,where the sleep apnea detection circuit 200 is reset again. However, if,at operation 1204, the microcontroller 202 determines that the voltagebeing supplied by the power supply is greater than the thresholdvoltage, the routine 1200 proceeds to operation 1208, where themicrocontroller 202 provides power to the dual-axis inclinometer 206.From operation 1208, the routine 1200 proceeds to operation 1210, wherethe microcontroller 202 receives, as an input, a pitch voltagecorresponding to a pitch angle relative to the z-axis 310 and a rollvoltage corresponding to a roll angle relative to the y-axis 308. Itshould be appreciated that the pitch voltage and roll voltage are merelyexamples of signals provided by the inclinometer 206.

From operation 1210, the routine 1200 proceeds to operation 1212, wherethe microcontroller 202 removes the power being supplied to theinclinometer 206. As part of polling the dual-axis inclinometer 206, themicrocontroller supplies power to the dual-axis inclinometer 206,receives signals from the dual-axis inclinometer, and then removes powerbeing supplied to the dual-axis inclinometer 206. In some embodiments,the microcontroller 202 may poll the dual-axis inclinometer 206 everytwenty seconds. The microcontroller 202 supplies power to the dual-axisinclinometer for approximately 0.25 seconds, during which time thedual-axis inclinometer 206 is capable of generating signalscorresponding to a current roll angle and pitch angle associated withthe subject's head relative to the y-axis 308 and the z-axis 310,respectively. After 0.25 seconds, the microcontroller 202 stopssupplying power to the dual-axis inclinometer 206, until afterapproximately 20 seconds, when the microcontroller 202 polls thedual-axis inclinometer 206 again. Since the microcontroller onlysupplies power to the dual-axis inclinometer 206 for approximately 1.2%(0.25 s/0.25 s) of the time that the apparatus 100 is operational, thebattery life of the apparatus 100 is approximately 81 times better thanany solution that requires the sensor, such as the dual-axisinclinometer 206, to be constantly powered on. For instance, using asensor to detect a current position of the subject's head by detectingthe movement of the subject's head requires the sensor to be constantlypowered on. In contrast, by polling the dual-axis inclinometer 206 inthe manner described herein can significantly improve battery life. Itshould be appreciated that the time between polling the dual-axisinclinometer 206 may be increased to further improve battery life. Inalternate embodiments, the microcontroller 202 may continuously supplypower to the dual-axis inclinometer 206, however, as explained above, acompromise on battery life.

From operation 1212, the routine 1200 proceeds to operation 1214, wherethe microcontroller 202 determines whether the signals from theinclinometer 206 representing the pitch angle and the roll angle liewithin the range of values. In some embodiments, the microcontroller 202determines whether the pitch voltage corresponds to a pitch angle thatlies between approximately 170° and 190° relative to the z-axis 310, andwhether the roll voltage corresponds to a roll angle that also liesbetween about 170° and 190° relative to the y-axis 308.

If, at operation 1214, the microcontroller 202 determines that eitherthe pitch angle or the roll angle do not lie within the thresholdvalues, the routine 1200 proceeds to operation 1216, where themicrocontroller 202 may generate an alarm indicating that the sleepapnea detection apparatus 100 is not calibrated. From operation 1216,the routine 1200 proceeds to operation 1218, where the subject mayadjust the orientation of the sleep apnea detection apparatus 100 withinthe subject's ear canal. In various embodiments, the adjustment mayinclude rotating the sleep apnea detection apparatus 100 within the earcanal of the subject. Alternatively, during a one time planaritycalibration, the adjustment may include rotating the sleep apneadetection circuit 200 within the interior chamber of the housing 110 byrotating the rotational component 138 of the sleep apnea detectionapparatus 100. From operation 1218, the routine 1200 returns back tooperation 1208, where the microcontroller 202 resumes the calibrationprocess by providing power to the inclinometer 206.

If, at operation 1214, the microcontroller 202 determines that the pitchangle lies between approximately 170° and 190° relative to the z-axis310 and the roll angle lies between approximately 170° and 190° relativeto the y-axis 308, the routine 1200 proceeds from operation 1214 tooperation 1220, where the microcontroller 202 may generate a stimulusindicating that the sleep apnea detection apparatus 100 has beencalibrated. In various embodiments, the stimulus may be a signal, suchas a 300 Hz signal that is generated for 3 seconds. From operation 1220,the routine 1200 proceeds to operation 1222, where the sleep apneadetection apparatus 100 may execute an apnea search algorithm, anembodiment of which is described with respect to FIG. 13.

FIG. 13 illustrates an exemplary logical flow diagram associated with anapnea search algorithm configured to detect whether the subject is in asleep apnea inducing position in accordance with some embodiments of thedisclosure. A routine 1300 begins at operation 1302, where themicrocontroller 202 provides power to the inclinometer 206. Fromoperation 1302, the routine 1300 proceeds to operation 1304, where theinclinometer 206 generates a pitch voltage and a roll voltagecorresponding to a pitch angle and a roll angle of a subject's head asexplained previously. It should be appreciated that inclinometer 206 maygenerate any type of signal including but not limited to, a voltage, acurrent, a charge, etc. From operation 1304, the routine 1300 proceedsoperation 1306, where the microcontroller 202 removes the power beingsupplied to the inclinometer 206. In various embodiments, themicrocontroller 202 may provide and remove power being supplied to theinclinometer 206 in an effort to conserve energy and extend the batterylife of the sleep apnea detection apparatus 100 as well as to minimizethe number of false alarms, during repositioning.

From operation 1306, the routine 1300 proceeds to operation 1308, wherethe microcontroller 202 determines the pitch angle and the roll anglebased on the signals received from the dual-axis inclinometer 206. Fromoperation 1308, the routine 1300 proceeds to operation 1310, where themicrocontroller 202 determines whether the pitch angle corresponds to asleep apnea inducing pitch angle position. In various embodiments, themicrocontroller 202 may determine that the pitch angle corresponds to asleep apnea inducing pitch angle position if the pitch angle liesbetween approximately 20° and 160° relative to the z-axis 310. If, atoperation 1310, the microcontroller 202 determines that the pitch angledoes not correspond to a sleep apnea inducing pitch angle position, theroutine 1300 proceeds to operation 1312, where the microcontroller 202sets a flag count to zero. In various embodiments, a flag count may be abit or a series of bits or any other data structure that may be used asa counter. From operation 1312, the routine 1300 proceeds to operation1324, where the microcontroller 202 waits until the microcontroller 202polls the dual-axis inclinometer 206 for new pitch and roll voltagereadings.

However, if at operation 1310, the microcontroller 202 determines thatthe pitch angle corresponds to the sleep apnea inducing pitch angleposition, the routine 1300 proceeds to operation 1314, where themicrocontroller 202 determines whether the roll angle corresponds to asleep apnea inducing roll angle position. In various embodiments, if theroll angle lies between approximately 25° and 155° relative to they-axis 308, the subject is in a sleep apnea inducing position.

If, at operation 1314, the microcontroller 202 determines that the rollangle does not correspond to a sleep apnea inducing roll angle position,the routine 1300 proceeds to operation 1316, where the flag count isreset to zero. In this way, if the subject is no longer in a sleep apneainducing position, a stimulus or alarm will not be activated. Fromoperation 1316, the routine 1300 proceeds to operation 1324, where themicrocontroller 202 waits until the microcontroller 202 polls thedual-axis inclinometer 206 for new pitch and roll voltage readings.

If, at operation 1314, the microcontroller 202 determines that the rollangle corresponds to a sleep apnea inducing roll angle position, theroutine 1300 proceeds to operation 1318, where the microcontroller 202increments the flag count by 1. From operation 1318, the routine 1300proceeds to operation 1320, where the microcontroller 202 determines ifthe flag count is equal to or greater than an alarm generation thresholdvalue. In some embodiments, the alarm generation threshold value may beset to 3. If, at operation 1320, the microcontroller 202 determines thatthe flag count is not equal to or greater than the alarm generationthreshold value, the routine 1300 proceeds to operation 1324, where themicrocontroller 202 waits until the microcontroller 202 polls thedual-axis inclinometer 206 for new pitch and roll voltage readings.However, if, at operation 1320, the microcontroller 202 determines thatthe flag count is equal to or greater than the alarm generationthreshold value, the routine 1300 proceeds to operation 1322, where themicrocontroller executes an alarm loop algorithm, which will bedescribed with respect to FIG. 14.

FIG. 14 illustrates an exemplary logical flow diagram for generating astimulus if the subject is in a sleep apnea inducing position inaccordance with some embodiments of the present disclosure. A routine1400 begins at operation 1402, where the microcontroller 202 sets in analarm counter to zero. From operation 1402, the routine 1400 proceeds tooperation 1404, where the microcontroller 202 sets stimuluscharacteristics or parameters corresponding to the alarm counter beingset to zero. From operation 1404, the routine 1400 proceeds to operation1406, where the microcontroller 202 generates a stimulus. As describedabove, the stimulus may be a sound, a voice command, a vibration orother haptic stimulus, or any other notification that a subject iscapable of sensing. It should be appreciated that the characteristics ofany stimulus generated by the transducer 216 may include, but are notlimited to, a frequency, an amplitude, and duration.

From operation 1406, the routine 1400 proceeds to operation 1408, wherethe microcontroller 202 increments the alarm counter by one. Fromoperation 1408, the routine proceeds to operation 1410, where themicrocontroller 202 determines if the pitch and roll angles correspondto the sleep apnea inducing positions. If, at operation 1410, themicrocontroller 202 determines that the pitch and roll angles do notcorrespond to a sleep apnea inducing positions, the routine 1400proceeds to operation 1412, where the microcontroller 202 executes thesleep apnea search algorithm, which is described herein with respect toFIG. 13. As described above, the microcontroller 202 may determine thatthe pitch and roll angles do not correspond to the sleep apnea inducingpositions if either the pitch angle does not lie between approximately20° and 160° relative to the z-axis 310, or if the roll angle does notlie between approximately 25° and 155° relative to the y-axis 308.

If, at operation 1410, the microcontroller 202 determines that the pitchangle and the roll angle correspond to a sleep apnea inducing position,the routine 1400 proceeds to operation 1414, where the microcontroller202 determines if the alarm counter is equal to 1. lf, at operation1414, the microcontroller 202 determines that the alarm counter is equalto 1, the routine 1400 proceeds to operation 1404, where themicrocontroller 202 sets alarm parameters corresponding to the alarmcounter being equal to one. In various embodiments, the alarm parameterscorresponding to the alarm counter being equal to 1 may be set togenerate a gentle, audible signal, such as a signal having a frequencyof approximately 30 Hz.

If, at operation 1414, the microcontroller 202 determines that the alarmcounter is not equal to 1, the routine 1400 proceeds to operation 1416,where the microcontroller 202 determines if the alarm counter is equalto 2. If, at operation 1416, the microcontroller 202 determines that theflag count is equal to 2, the routine 1400 proceeds to operation 1404,where the microcontroller 202 sets alarm parameters corresponding to thealarm counter being equal to 2. In various embodiments, the alarmparameters corresponding to the alarm counter being equal to 2 may beset to generate a slightly more unpleasant audio signal, such as asignal having a frequency of approximately 100 Hz having a duration of0.5 seconds.

If, at operation 1416, the microcontroller 202 determines that the alarmcounter is not equal to 2, the routine 1400 proceeds to operation 1418,where the microcontroller 202 determines if the alarm counter is equalto or greater than 3. If, at operation 1416, the microcontroller 202determines that the flag count is equal to or greater than 3, theroutine 1400 proceeds to operation 1404, where the microcontroller 202sets alarm parameters corresponding to the alarm counter being equal toor greater than 3. In various embodiments, the alarm parameterscorresponding to the alarm counter being equal to 3 may be set togenerate an even more unpleasant audio signal, such as a signal having afrequency of approximately 300 Hz for a duration of 0.5 seconds. As thealarm counter increases beyond 3, the alarm parameters may be set togenerate a stimulus that is similar to an alarm clock. In oneembodiment, the stimulus may have a frequency of approximately 300 Hzand may pulsate indefinitely with a duration of 1 second and gaps of0.25 seconds. It should be appreciated that the alarm parametersassociated with higher alarm counters may generate audible signals orother stimuli that are progressively more distracting than alarmparameters associated with lower alarm counters. For instance, the alarmparameters associated with an alarm counter of 3 may be louder, longerand have a different harmonic content than the alarm parametersassociated with the alarm counter of 2 or the alarm counter of 1. Itshould be appreciated that the routine 1400 may end once the subject isno longer in a sleep apnea inducing position. In some embodiments, themicrocontroller may be programmed to generate signals that correspond toa noise having particular characteristics or audio files having formats,including but not limited to, .mp3, .wav, .wma. Transducer 212 may alsobe implemented with a tactile for haptic stimulus generator, such asvibratoring mechanism which, when activated, creates a detectablevibrations, the parameters of which may be manipulated if the device issequentially activated to create increasingly stronger stimulus untilthe subject reacts.

Referring now to FIG. 15, a plot 1500 of various readings correspondingto the pitch angle, the roll angle, and an output signal generated bythe microcontroller 202 when the subject assumes the six supinepositions that maximize the effects of apnea is shown. The six supinepositions that maximize the effects of apnea include 1) laying flat onback with no head elevation and face up; 2) laying flat on back with nohead elevation and head turned as far as possible to the left; 3) layingflat on back with no head elevation and head turned as far as possibleto the right; 4) laying flat on back with elevated head face up; 5)laying flat on back with elevated head and head turned as far aspossible to the left; and 6) laying flat on back with elevated head andhead turned as far as possible to the right. In various embodiments, thepitch angle formed by the elevated head is 115°. In particular, the plot1500 shows a pitch signal 1502 that corresponds to the pitch angle ofthe subject's head relative to the horizontal axis 308, a roll signal1504 that corresponds to the roll angle of the subject's head relativeto the y-axis 308, and an output signal 1506 that corresponds to thegeneration of a stimulus when the subject's head is in a sleep apneainducing position. As shown in the plot 1500, the output signal 1506indicates that a stimulus was generated in each of the six supinepositions that maximize the effects of apnea.

Referring now to FIG. 16, a plot 1600 of various readings correspondingto the pitch angle, the roll angle, and an output signal generated bythe microcontroller 202 when the subject assumes six non-supinepositions that minimize the effects of apnea is shown. The sixnon-supine positions that minimize the effects of apnea include 1)laying flat on stomach with no head elevation and face down; 2) layingflat on stomach with no head elevation and head turned as far aspossible to the left; 3) laying flat on stomach with no head elevationand with head turned as far as possible to the right; 4) laying flat onstomach with head elevation and face down; 5) laying flat on stomachwith head elevation and head turned as far as possible to the left; and6) laying flat on stomach with head elevation and head turned as far aspossible to the right. In various embodiments, the pitch angle formed bythe elevated head is 115°. In particular, the plot 1600 shows a pitchsignal 1602 that corresponds to the pitch angle of the subject's headrelative to the z-axis 310, a roll signal 1604 that corresponds to theroll angle of the subject's head relative to the y-axis 308, and anoutput signal 1606 that corresponds to the generation of a stimulus whenthe subject's head is in a sleep apnea inducing position. As shown inthe plot 1600, the output signal 1606 indicates that no stimulus wasgenerated in any of the six non-supine positions that minimize theeffects of apnea.

Although the present disclosure provides methods for detecting sleepapnea, the disclosed system and technique should not be limited tospecific implementations described herein. Rather, the presentdisclosure may relate to detecting other conditions, such as sleepwalking, sudden infant death syndrome (SIDS), as well as an operator ofa vehicle falling asleep. To implement the use of the sleep apneadetection apparatus in any of these conditions, the microcontroller mayneed to be programmed to determine when the pitch and roll anglesassociated with the subject's head corresponds to specific parametersassociated with sleep walking, SIDS, or falling asleep during theoperation of a vehicle. Note also that the sampling time of thealgorithm may be optimized for each application.

In addition, the disclosed system and technique should not be restrictedto any specific implementations here described, for which otherbeneficial or alternate implementations may be substituted, in order tosatisfy the organizational, functional or technology requirementsimposed upon this disclosed system by any implementer. It will beapparent to those skilled in the art that modifications to the specificembodiments described herein may be made while still being within thespirit and scope of the teachings disclosed herein.

What is claimed is:
 1. A device for detecting sleep disorderscomprising: a housing insertable into an ear canal of a subject; asensor disposed within the housing and configured to measure a positionof the subject's head relative to an axis of gravity; a transducerresponsive to the sensor for creating a stimulus detectable by thesubject.
 2. The apparatus of claim 1 wherein the transducer is disposedwithin the housing.
 3. The apparatus of claim 1 wherein the sensorcomprises an inclinometer.
 4. The apparatus of claim 1 wherein thesensor measures a pitch angle of the subject's head relative to the axisof gravity.
 5. The apparatus of claim 1 wherein the sensor measures aroll angle of the subject's head relative to a horizontal axisorthogonal to the axis of gravity.
 6. The apparatus of claim 1 incombination with a processor located within the housing, the processoroperably coupled to a transmitter and the transducer.
 7. The apparatusof claim 1 wherein the transducer generates haptic stimulus.
 8. Theapparatus of claim 1 wherein the transducer generates an audiblestimulus.
 9. A device for detecting sleep disorders comprising: ahousing; a gravitational sensor disposed within the housing andconfigured to generate signals corresponding to a measurement of aposition of a subject's head relative to an axis of gravity; and atransducer responsive to the signals generated by the gravitationalsensor and configured to create stimulus detectable by the subject. 10.The apparatus of claim 9 wherein the gravitational sensor comprises adual-axis inclinometer.
 11. The apparatus of claim 9 in combination witha controller disposed within the housing responsive to the signalsgenerated by the gravitational sensor.
 12. The apparatus of claim 9wherein the transducer generates at least one of haptic stimulus andaudible stimulus.
 13. The apparatus of claim 9, further comprising acontroller, the controller further comprising: program logic to receivesignals from the gravitational sensor corresponding to the position ofthe subject's head relative to the axis of gravity, program logic todetermine a pitch angle of the subject's head relative to the axis ofgravity and to determine a roll angle of the subject's head relative toa horizontal axis orthogonal to the axis of gravity, program logic tocompare the determined pitch angle and roll angle to a predefined rangeof threshold pitch angles and predefined range of threshold roll angles,and program logic to cause the transducer to generate the stimulus ifthe determined pitch angle and roll angle of the subject's head lieswithin the predefined range of threshold pitch angles and the predefinedrange of threshold roll angles.
 14. A method for detecting sleepdisorders comprising: a) measuring with a sensor, a position of asubject's head relative to an axis of gravity; b) modifying a flag countif the subject's head is in a sleep apnea inducing position based on ameasurements from the sensor; C) repeating a)-b); and c) alerting thesubject with stimulus when the flag count at least equals apredetermined threshold.
 15. The method of claim 14 wherein c)comprises: c1) generating one of an audio and haptic stimulus detectableby the subject.
 16. The method of claim 14 wherein a) comprises: a1)measuring one of a roll and pitch angle of the subject's head relativeto the axis of gravity.
 17. A device for detecting sleep disorderscomprising: a housing insertable into the ear canal of a subject; asleep apnea detection circuit disposed within the housing comprising asensor configured to measure a pitch angle relative to an axis ofgravity and a roll angle relative to a horizontal axis orthogonal to theaxis of gravity, and a controller configured to determine whether thesubject is in a sleep apnea inducing position based on the pitch angleand the roll angle; and a transducer responsive to the controller forcreating a stimulus detectable by the subject.
 18. The device of claim17 wherein the sleep apnea inducing position is defined by a range ofroll angles formed between approximately 25° and 155° relative to ahorizontal axis orthogonal to the axis of gravity and by a range ofpitch angles formed between approximately 20° and 160° relative to theaxis of gravity.
 19. A system for detecting and treating sleep disorderscomprising: A) a housing; B) a dual-axis inclinometer disposed withinthe housing capable of measuring a pitch angle and a roll angle of thesubject's head relative to an axis of gravity; C) circuitry configuredto: receive signals from the gravitational sensor corresponding to theposition of the subject's head relative to the axis of gravity,determine a pitch angle and a roll angle of the subject's head relativeto the axis of gravity, compare the determined pitch angle and rollangle to a predefined range of threshold pitch angles and predefinedrange of threshold roll angles, and cause the transducer to generate thestimulus if the determined pitch angle and roll angle of the subject'shead lies within the predefined range of threshold pitch angles and thepredefined range of threshold roll angles; and D) a transducerresponsive to the sensor for creating a stimulus detectable by thesubject.
 20. The device of claim 19 wherein the predefined range ofthreshold roll angles extend between approximately 25° and 155° relativeto a horizontal axis orthogonal to the axis of gravity and thepredefined range of threshold pitch angles extend between approximately25° and 155° relative to the axis of gravity.
 21. A method for detectingsleep disorders comprising: A) providing a system comprising: i) ahousing insertable into the ear canal of a subject, ii) a sensordisposed within the housing and capable of measuring a pitch angle and aroll angle of the subject's head relative to an axis of gravity, iii) acontroller responsive to signals from the sensor, and iv) a transducerresponsive to the sensor for creating a stimulus detectable by thesubject; B) receiving signals from the sensor corresponding to theposition of the subject's head relative to the axis of gravity, C)determining a pitch angle and a roll angle of the subject's headrelative to the axis of gravity, D) comparing the determined pitch angleand roll angle to a predefined range of threshold pitch angles andpredefined range of threshold roll angles, E) modifying a flag count ifthe determined pitch angle and roll angle of the subject's head lieswithin the predefined range of threshold pitch angles and the predefinedrange of threshold roll angles, F) determining if the flag count atleast equals a predefined threshold, G) upon determining that the flagcount at least equals the predefined threshold flag count, causing thetransducer to generate stimulus, and H) repeat B)-G) after a predefinedtime interval.
 22. The method of claim 21 further comprising: I)resetting the flag count if the determined pitch angle or roll angle ofthe subject's head do not lie within the predefined range of thresholdpitch angles and the predefined range of threshold roll angles.
 23. Themethod of claim 21 wherein the sensor and the transducer are located inthe housing.
 24. The method of claim 21 wherein the controller islocated remotely from the housing.
 25. A sleep apnea detection apparatuscomprising: a sensor attachable to a subject's head for detecting anangular position of the subject's head relative to an axis of gravity;and a transducer responsive to the sensor for creating a stimulusdetectable by the subject.
 26. A method for detecting sleep disorderscomprising: a) estimating the percentage of closure of a subject'sairway from the angular position of the subject's head relative to anaxis of gravity; and b) causing a transducer to generate stimulus if theposition of the subject's head lies within the predefined range ofpositions determined to cause a sleep disorder.